Scarifier for use with asphalt concrete roadway refinishing apparatus

ABSTRACT

The embodiment of the invention disclosed herein is directed to a scarifier assembly for use with an asphalt concrete roadway refinisher. The scarifier has a support frame for movement in a given direction over the road surface being refinished, and the plurality of scarifing blades secured to the support frame for selective upward and downward movement to engage the road surface when in the down position during the scarifing operation for digging up and excavating the road surface after it is heated with radiant heat energy. The scarifier assembly is urged against the heated road surface by the air bags which force the scarifing blades deep into the asphalt pavement. The scarifing blades are secured by shear pin means which can be easily replaced when necessary.

United States Patent [1 1 Cutler 1 Sept. 23, 1975 [75] Inventor: Earl F. Cutler, Lawrence, Kans.

[73] Assignee: Cutler Repaving, Inc., Lawrence,

Kans.

[22] Filed: May 6, 1974 1211 Appl. No.: 467,067

[52] U.S. Cl 404/90; 404/95 [51] Int. Cl? E01C 23/14 [58] Field of Search 404/90, 95, 91, 92, 93, 404/76 [56] References Cited UNITED STATES PATENTS 1,472,888 11/1923 Rose A 404/90 X 1,523,084 1/1925 Scheunemann.. 404/90 2,196,205 4/1940 Flynn 404/90 2,254,463 9/1941 Wells et a1. 404/95 2,747,475 5/1956- West 404/91 3,361,042 1/1968 Cutler 404/90 OTHER PUBLICATIONS Caterpillar Publication AEO44369, 10/73.

Primary ExaminerMervin Stein Assistant Examiner-Steven Hawkins Attorney, Agent, or FirmOlson, Trexler, Wolters, Bushnell & Fosse, Ltd.

[57] ABSTRACT The embodiment of the invention disclosed herein is directed to a scarifier assembly for use with an asphalt concrete roadway refinisher. The scarifier has a support frame for movement in a given direction over the road surface being refinished, and the plurality of scarifing blades secured to the support frame for selective upward and downward movement to engage the road surface when in the down position during the scarifing operation for digging up and excavating the road surface after it is heated with radiant heat energy. The scarifier assembly is urged against the heated road surface by the air bags which force the scarifing blades deep into the asphalt pavement. The scarifing blades are secured by shear pin means which can be easily replaced when necessary.

25 Claims, 8 Drawing Figures US Patent Sept. 23,1975 Sheet 1 of4 3,907,450

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US Patent US Patent Sept. 23,1975 Sheet 4 Of4 3,907,450

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wklw NR VN R R w ww BACKGROUND OF THE INVENTION,

This invention relates generally to improvementsin structure and apparatus roadway resurfacing machincry, and more particularly to a new and improved scarifing' assembly which forms one'of thework stations'of the roadway resurfacingmachine. I i

This invention dealsv with substantial useful improvements in my earlier filed patent applicationgentitled Road Surfacing Apparatus and whichhas issued as US. Pat. No. 3,361,042. This patent discloses means for quickly and inexpensively resurfacing roadways which are made of asphalt concfete material and the like. The apparatus may be in the order; of about 8 to 12 feet wide and 40 to 50 feet long and move along the roadway at a relatively slow rate so that during a single continuous pass the old road surface in front of the machine isheated and ultimately. excavated .asthe rnachine moves thereover and a refinished road, surface is formed at the rearof the machine. All of the old road surface material is .recycled into the new r oad surface thus formed..A distinct advantage of repaving apparatus of the type disclosed in my. earlier patent is that the finished repaved roadsurface, is substantially immediately available for traffic within a matterhof minutes after the completion of the road surface. ,Q

- Heating apparatus as disclosed in my co-pending application Ser. No. 369,775 filed June 13,..1-973, substantially'increases the efficiency of heatingthe road surface as the machine moves thereacro ss Therefore, scarifing equipment can excavate the heated asphalt to a greater depth so that more complete mixing of filler asphalt is obtained. e

Heretofore, asphalt concrete roadway repaving machines have been relatively long because, ofthe necessity of the plurality of successive work stations along the machine. Furthermore, to effect adequate scarifing of the old road surface, several scarifing stations had to be used.

SUMMARY [OF THE INVEN ION v i Accordinglyyit is an object of this invention to provide a new and improved scarifing assembly to be positioned adjacent radiant heating elements of an asphalt concrete roadway repaying machine whichca'rrexcavate the road surface to a sufficientdepth, thereby eliminating the need of two ormorescarifing assemblies. Y I

Still another object of this invention isto'provide a new and improved scarifing assemblyfor use'with asphalt concrete roadway repaving machines which can be repaired quickly and'easily'should the scarifing blades inadvertently be' come dislodged from their fixed position.

Still another object of this invention "is to provide a new and improved scarifing assembly which receives pressure from airbags so as urge the'scarifingblades directly downwardly .against'theroad' surface to be excavated. I

Many other objects, features and advantages of this .invention will be irnore fully realizedand understood '30= .I,- 7 I I DETAILED DESCRIPTION OF THE ILLUSTRATED of the'drawings are intended to designate similar elements or components. 1

, BRIEF DESCRIPTION oF THE DRAWlNGS 'FIG. 1 is 'a side elevational view of a'road repaving machine wherein the scarifing assembly of this invention'is utilized; I 1

' FIG. 2 is a fragmentary detailed showing of the scarifing a'ssembly'o'f this invention;

FIG. '3 is a fragmentary perspective view of the scarifing assembly of this invention;

-' FIG. 4 is a fragmentary side view showing the pivotal -shear arrangement for the scarifing blades of the scarifing assembly of this invention;

FIG. 5 is a front 'view of the scarifing blades of FIG.

4 I v a.

FIG. 6 is a top view showing thestaggered row arrangement of the scarifing blades of the scarifing assembly of this invention;

FIG. 7 is adiagrammatic representation showing the control valve manifold arrangement for controlling a plurality of air bags to urge the scarifing blades into contact with the road surface in accordance with the principles of this-invention; and

25 FIG. 8 is a top view illustrating the transverse arrangement of'a plurality of support arm members, each having a group of scarifing blades associated therewith to be urged into contact with the road surface being EMBODIMENT Referring now to FIG. 1, there is seenan elevational view of a roadresurfacing machine designatedgenerally'by' referencenurneral 10,.and whereinthe scarifing assembly of this'invention is utilized. The road resurfacing machine- 10 has a plurality of large pneumatic tires"l3 having sufficient contactarea with the road surface so that the weight of the large machine is distributed uniformly over the road surface so as not to deform the newly paved roadway passing therebeneath. 'As. the road resurfacing machine 10 moves forward over a damaged road surface, the front end: of the machine will heat up the road surface to a depth of approximately 1 to 2'inches or more and an intermediate stage of the machine','where at the scarifing assembly of this invention is located, will dig-up the road surface. Thequantity of old road surface now forming loose pavement has a quantity of new asphalt-material added therewith to build up the road surface to the previous -'heightor to a height greater than the old road surface, if desired. Generally, the quantity of new asphalt material added to the old road surface is just enough'to replace those quantities which have been depleted as a result'of pot holes or the like. The rate of travel of the machine may be on the order of 8 to feet per minute v thereby providing a completely reconstructed road; surface upon which trafficcan travel'substantially immediately after the road surface has bee formed.

A quantity'of new asphalt material l4=is delivered via atruck or othersuitable'transport means 16 into a hopper or receptacle l7'located at the front of the road resurfacing machine '10. A conveyor assembly 18 along the top portion ofthe frame support of the machine transports the new asphalt material from the hopper to "one or more various work stations along the machine.

' A control station designated generally by reference nufunctions to-be accomplished during'the travel of the preferably by independent hydraulic motors operated by hydrostatic hydraulic supply pumps controlled by the diesel engines and control panel 2.0a. However, it willbe understood thatother drive means thanthose described here may be incorporated. l A plurality of fuel tanks 21 are mounted on top of the support frame and designated generally-by reference numeral 22 and'are used to carry fuel supplies for both the'die'sel engine and the, radiant heating apparatus. 2 4 which is located at the. forward .endrof the machine. While a single radiantsheating apparatus 24- is disclosed hereinpprevious disclosuresof this rn achine .in related patent applications disclosed two radiant heating'apparatus. Therefore, it will beunderstood .that one, two. or more heating units may be utilized without departing from the spiritand scope of this invention. One or more bf the fuel tanks 21 may be filled with diesel-fuel while one or more of the other fuel tanks may be filled with pentanefuel for operating the radiant'heatingbur-ners within the heater 24.The manner in which the road resurfacing machine. l-operates is mo e .fully disclosed in my related U.S.--Pat. No. 3,361,042; and no:further details of description of operation isdeemed necessary *hereina However, the details necessary for a complete understanding of this invention areafunderstood to. be incorporated herein from the abovegrnentioned patent. The heating apparatus 24 includes aheating chamber '28 facing downwardly to be positionedimmediately over the road surface-tobe .repaved so that. the road surface can be heated to a depth of approximately two inches more 'orless-so that the asphalt of the concrete pavement can be adequately softened to be. excavated by the scarifingapparatus of this. invention. After the heating of the road surface is accomplished, a scarifing assembly.-25', positioned behind theheating apparatus,

-' will excavatethe road surface to v a desired depth. The scarifing apparatus 25is of new and novel design and is substantially more efficientthan scarifing apparatus heretofore'utilizedq l I FIG. 2-illustrates a side'elevational view of the scarifing apparatus 25 and shows onlya portion of a support frame adapted to be moved overthe road surface in a'given direction as indicated-by the arrow 31. Positioned beneath the support frame, 30 are a plurality of scarifing blades32 which are-formed in a plurality of sub-groups extending transversely across the direction of motion of the machine. Eachpf the sub-groupsof scarifing blades 32..aresecured to the free endof an "-arm member33 tentatively secured by pin means 34 to a depending pull bar assembly 36 that raises and lowers by a motor driven drivescrew mechanism designated generallyby reference numeral 37.- The .drive screw .mechanism, 37 therefore isused to adjust the relative 4 positionof the pull bar assembly 36 so that the arms 33 are maintainedsubstantiallyin a parallel position over the road surface. thereby eliminating the possibility of bending of th e 'arms under the forces of the'scarifing operation.

r Most advantageously. pressure applying means designated generally by reference numeral 38 are positioned beneath the support frame 30 and are in direct engage-j ment with the free ends of the arms 33 so that downward pressure is applied directly to the sc arifingblade's' duringthe scarifing operation. T he pressure applying means 38 iss ecu red to a pressure bar member 39 which also holds a pluralityof airbags 40, each air bag engagingthe free end of the associated arm member 33, as best seen in FIG. 8. While the number of arms and ass'ociated air bags is here illustrated as being 12, designated generally by reference numerals3'3 a, 33b, 33b, 33d, 33?, 33f, 33 33h, 331', 33 33k and 331 and'the air bags designated by 4011,4011, 40c, 40d, 40, 40f, 403;, 40/1, 40i, 4 0j, 40k, and 40l, a detailed description of only a singlesupport arm and air bag configuration will be given herein, it being understood that the sai'neclescription'afpplies to all other arms andair bags.- I

The pressure bar 38 is secured to the frame member pivot'means 41," located at each'end thereof so that'the pressure barcan be aligned with the inclination of theroad siirface'; if desired. The pressure bar struc- "ture 38 ismoved upwardly and downwardly=relative to effecting excavation of the road surface is obtained fro'mthe air' bag 40 which has an air line 44 connected thereto. The air line 44 applies pressure to the bag from a regulated air supply within a manifold, to be describedin'more detail herein below.

Positioned immediately behind the scarifing blades 32 andslightly. to the outside thereof are a pairof joint cutting blades which remove the excess mix of asphalt concrete from the seam formed along the side of the machine. There is one of these joint cutting blades 46 on each side of the machine and 'is adjustable by a pair of link members 47 and 48 connected to. a boss 49 and to a support arm 50. Theadjustmentis made by a .threaded shaft.51. Preferably the lower edge surface 46a of the joint cutting blade issupplied with aweld beadof hard surfacing metal. V g I The excavatedasphalt concrete is here designated generally by reference numeral 52 and is made level by a a leveling blade 53 which rotates about a central axis 54 bysuitable side border means, not shown. The leveling. blade 53. is adjustable upwardly and downwardly by vsuitable meansindi'cated generally by reference numeral 56. Therefore, the level of loose asphalt concrete is maintained uniform across the width of the machine prior to compressing the same into a compact road surface. v

When pressure from within the air bag 40 is removed each of the,arrn members 33 is biased upwardly'by a leaf spring member 57 which has one end thereof s e'-. cured thereto the pull bar 36 and theother endthereof placed beneaththe pad element 58 welded to the'underside of the arm 53. FIG. 3 clearly illustrates the type I of construction ofieach of the arm members33, they being all substantially the s'ame across the machine.

The arm member 33 is formed by a pair of spaced apart steel channel members 59 and 60 with the tab member 58 welded therebetween and theleaf spring 57 passes through the space between the channel members to engage the pad, as seen in FIG. 3. This feature of construction is also seen in FIG. 8.

The free end of the arm members 33 are provided with upper and lower plates 60 and 61, respectively, to form a substantially rigid box type construction to support the group scarifing blades secured ther eto. The scarifing blade configuration is best illustrated in FIG. 6 which shows them arranged in rows 63, 64 and 65 which are staggered relative to one another, as seen in the drawing, so that the average spacing between scarifing blades is relatively small when considering the closest adjacent blade of a next r'ow'but which allows sufficient space between the blades of a given row so that excavated asphalt concrete material can easily flow through the scarifing apparatus to the leveling wheel 53. This arrangement eliminates the usual buildup of asphalt material in front of the scarifing blades and provides for a more uniform admixture to be produced.

FIGS. 4 and 5 illustrate the details of construction of the scarifing blades secured to the free end of the support arms 33. Each of the scarifing blades are here designated by reference numeral 70 and are secured between a pair of parallel spaced apart support plates 71 and 72. The scarifing blades 70 are held in position between the support plates 71 and 72 by a pair of bolt members 73 and 74, the bolt member 73 being of a larger diameter than the bolt member 74. Also the bolt member 74 is of a material that will shear under a predetermined amount of force so that should the scarifing blades 70 inadvertently engage an immovable structure in the road surface, such as a manhole, the smaller diameter bolt member 74 will shear and the scarifing blade will pivot about the larger diameter bolt member 73, as illustrated in phantom lines in FIG. 4. The repair and maintenance of this type of structure is relatively simple in that it only requires anew shear bolt to be in serted through the plate members 71 and 72 and the scarifing blade 70. The plate-members are secured to I the bottom of the plate 61 by suitable welding techniques and are held by welds 74. The lowermost leading edge of each of the scarifing blades 70 is provided with a hard material insert 76, such as tungsten carbide or the like.

FIG. 8 clearly illustrates the arrangement of the support arms 33 together with their groups of scarifing blades 32 and associated air bags positioned between the-ends of the arm and the pressure bar 38. In this Figure, it'will be noted that the endmost arm members 33a and 331 together withtheir associated scarifing blades 32a and 321 receive a different: amount of pressure than do the scarifing blades and arms 33b through 33k. One reason for the additional force is the use of the joint cutting blades 46 at these locations. This is achieved by connecting the air bags a and-401 together and to one flow control manifold and connecting the air bags 40b through 40k to another flow control manifold. g l

The manifold arrangement to'achieve proper control of air pressure to the air bagsand 401 is illustrated in FIG. 7. Here a manifold unit 80 is divided into two manifold sections, 81 and 82, which are each individually controlled by separate pressure regulator units 83 and 84, respectively. The pressure regulators 83 and 84 are fed from a common pressure line 86. It is sometimes desirable to apply more pressure to the endmost air bags 40a and 401 so as to effect a deeper penetration of scarifingof the road surfacing by the associated scarifing blades 32a and 321. Therefore, the manifold chamber 81 is maintained at a higher pressure than is the manifold chamber 82. The flow control valves associated .with the manifold unit 80 are of the on/off'or open/close type, each being designated generally by reference numeral 86. The output line 87 associated with each of the valves is connected directly to its associated air bag and will inflate the air bag to a pressure determined by the associated regulator 83 or 84. If it is desired to raise selected ones ofthe arm members 33a-33l, so as to bypass a manhole cover or the like, the air flow control valves 86 associated with the appropriate air bags 40 will be opened so that no pressure will be applied to the air bag, and the chamber within the airbag is opened to atmospheric pressure. Once the repaving apparatus has passed over the manhole .cover the appropriate air, bags are again inflated to the pressure desired by operating the flow control valve 86.

What has been described is a simple and efficient scarifing'assembly to use in conjunction with road paving apparatus which substantially improves the scarifing operation so that only a single scarifing unit is now required on the apparatus. While a single specific embodiment of this invention has been illustrated herein, it will be understoodthat variations and modifications of the invention may be effected without departing from the spirit and scope of the novel concepts as set forth'in the specification and claims.

The invention is claimed as follows:

1. A scarifier assembly for engagement with a road surface to excavate the road surface, comprising: a support frame adapted to be moved over the road surface in a given direction, a plurality of scarifying blade units secured to said support frame for separate selective upwardand downward movement and positioned to have cutting tips thereof engageable with the road' surface when in the down position during a scarifying operation, and a plurality of discrete 'yieldable fluid operated pressure applying means positioned beneath said sup port frame and directly over said-plurality of scarifying 'blades to apply a downward pressure directly upon said scarifying blades during the sacrifying operation. I

2. The scarifier assembly for engagement with a road surface to excavate the road surface asset forth'in claim 1 wherein said plurality of scarifying blade units comprise groups of blades in arowacro ss said support frame, said row being transverse to the direction of travel of said support frame.

3. The scarifier assembly for assembly with the road surface to excavate the road surface as set forth'in claim 1 wherein each of said discrete yieldable pressure units is an air bag.

4. The scarifier assembly for engagement with the road surface to excavate the road surface as set forth in claim 1 wherein each of said groups of scarifying blades is formed of three rows of three blades in each row aligned transversely to the direction of travel of said support frame and each row staggered from the other rows to allow excavated road material easily to pass through the scarifying blades as it travels in said given direction. v i v 5. The scarifier assembly for engagement with the road surface to excavate the road surface as set forth in claim 1 further including fluid pressure control means for controlling the pressure producedby each of the said plurality of discrete yieldable pressure units, said pressure control means including means for controlling the fluid pressure produced by the two endmost discrete yieldable pressure units independent of the discrete yieldable units therebetween.

I 6. The scarifier assembly for engagement with the road surface to excavate the road surface as set forth in'claim 5 wherein said discrete pressure units between said two endmost units are operated from a common pressure supply, and including valve means connected between said common pressure supply and said discrete yieldable pressure units, whereby selected ones of said pressure units can be deactivated.

7. The scarifier assembly for engagement with a road surface to excavate the road surface as set forth in Claim 1 wherein said scarifying blades include shear pin means for holding said scarifying blades in a fixed position during a scarifying operation and to permit rearward pivotal movement of said scarifying blade when a predetermined high shear pressure is exerted on said scarifying blade.

8. The scarifier assembly for engagement with a road surface to excavate the road surface as set forth in claim 1 further including joint cutting blade means positioned transversely outwardly of the endmost scarifying blades to remove road resurfacing material from the seamformed along the transverse edges of a repaved road surface to be formed.

cutting tip insert element of hardened metal.

10. A scarifier assembly for engagement with a road surface to excavate the road surface, comprising: a support frame adapted to be moved over the road surface in a given direction, a plurality of scarifying blades secured to said support frame for selective upward and downward movement and positioned to have cutting tips thereof engageable with the road surface when in I the down-position during a scarifying operation, yieldable pressure applying means positioned beneath said upon said scarifying blades during the scarifying operation, a plurality of arm means each having one end piv otally secured to said support frame, said plurality of scarifying blades being arranged in groups, each group secured to the free end of an independent one of said plurality of arm means, a pressure beam secured to said support frame immediately above said free end of said arm means, and pressure bag means positioned between said pressure beam and said free end of said arm means to urge the scarifying blades into the road surface being excavated. a

1 1. The scarifier assembly for engagement with the road surface to excavate the road surface as set forth in claim 10 further including a plurality of paired spaced apart support plates depending from said free end of said arm means, said scarifying blades being positioned between said support plates, a first fastener of predetermined diameter passing through said support plates and the upper end of said scarifying blade, a second fastener of a diameter less than said predetermined whereby an excess of pressure applied to said scarifying blade will shearsaid second diameter fastener and pivot the scarifying blade about said first fastener.

12. The scarifier assembly for engagement witha road surface to excavate the road surface as set forth in claim 1 1 further including a plurality of spring means for automatically biasing said arms upwardly to raise the scarifying bladefrom the road surface when the pressure applying units are deactivated. I I3. The scarifier assembly for engagement with a road surface to excavate the road surface as set forth in claim 12 wherein said spring means are a plurality of discrete leaf springs for each one of said arm means.

14. A road scarifier apparatus for excavating a road surface comprisingin combination: heating means for' movement over the road surface to soften asphalt concrete pavement forming the road surface, a support :frame for supporting said heating means, said support frame adapted to be moved over the road surface in a given direction, a plurality of scarifyingblade units secured to said support frame behind said heating means for separate selective upward and downward movement and positioned to have cutting tips thereof engageable with the heated road surface when in the down position for excavating the road surface, and a plurality of discrete separately yieldable fluid operated pressure applying units positioned beneath said support frame and respectively directly over said plurality of scarifying blade units separately to apply a downward pressure directly upon the scarifying blade units during a scarifying operation.

15. The road scarifier apparatus for excavating a road surface as set forth in claim 14, further including fluid pressure control; means for controlling the pressure produced by each of said yieldable plurality of discrete pressure units, said pressure control means including means for controlling the pressure produced by the two endmost discrete yieldable pressure units independent of the discrete pressure units therebetween.

16. The road scarifier apparatus for excavating a road surface as set forth in claim 15, wherein said discrete yieldable pressure units between said two endmost units are operated from a common pressure supply, and includingvalve means connected between said common pressure supply and said discrete yieldable pressure units, whereby selected ones of said pressure units can be de-activated. 4

17. The road scarifier apparatus for excavating a road surface as set forth in claim 14, wherein said scarifying blades include shear pin means for holding the scarifying blades in a fixed position during a scarifying operation and to permit rearward pivotal movement of the scarifying blades when a predetermined high shear pressure'is exerted on the scarifying blades.

18. The road scarifier apparatus for excavating a road surface as set forth in claim 14 wherein each of said discrete pressure units is an air bag.

19. The road scarifier apparatus for excavating a road surface as set forth in claim 14, further including joint cutting blade means positioned transversely outwardly of the endmostscarifying blades to remove the road resurfacing material from the seam formed along the transverse edges of the repaved road surface formed by said apparatus.

20. The road scarifier apparatus for excavating a road surface as set forth in claim 14, wherein said scarifying blades each include a cutting tip insert element of hard metal.

21. A road scarifier apparatus for excavating a road surface comprising in combination: heating means for movement over the road surface to soften asphalt concrete pavement forming the road surface, a support frame for supporting said heating means, said support frame adapted to be moved over the road surface in a given direction, a plurality of scarifying blades secured to said support frame behine said heating means for selective upward and downward movement and positioned to have cutting tips thereof engageable with the heated road surface when in the down position for excavating the road surface, yieldable pressure applying means positioned beneath said support frame and directly over said plurality of scarifying blades for applying a downward pressure directly upon the scarifying blades during a scarifying operation, a plurality of arm means each having one end thereof pivotally secured to said support frame, said plurality of scarifying blades being arranged in groups, each group secured to the free end of an independent one of said plurality of arm means, a pressure beam secured to said support frame immediately above said free end of said arm means, and pressure bags positioned between said pressure beam and said free end of said arm means to apply pneumatic pressure between said pressure means and the end of said arm means to urge the scarifying blades into firm contact with the road surface being excavated,

22. The road scarifier apparatus for excavating a road surface as set forth in claim 21 further including a plurality of paired spaced apart support plates depending from said free end of said arm means, said scarifying blades being positioned between said support plates, a first fastener of predetermined dimension passing through said support plates and the upper end of said scarifying blade, a second fastener of a dimension less than said predetermined dimension passing through said support plates and said scarifying blade immediately below said fastener, whereby an excess of pressure applied to said scarifying blade will shear said second fastener and pivot the scarifying blade about said first fastener.

23. The road scarifier apparatus for excavating a road surface as set forth in claim 22 further including a plurality of spring means for automatically biasing said arms upwardly to raise the scarifying blades from the road surface when the pressure applying units are de-activated.

24. The road scarifier apparatus for excavating a road surface as set forth in claim 23, wherein said spring means are a plurality of discrete leaf springs, each leaf spring associated with its associated arm means.

25. The road scarifier apparatus for excavating a road surface as set forth in claim 15, which includes fluid pressure control means associated with said yieldable pressure control means, said pressure control means having means to control the pressure of the endmost units of the scarifying blades independent of control of the units therebetween, said control means further including means for deactivating selected ones of said plurality of units including said endmost units of scarifying blades. 

1. A scarifier assembly for engagement with a road surface to excavate the road surface, comprising: a support frame adapted to be moved over the road surface in a given direction, a plurality of scarifying blade units secured to said support frame for separate selective upward and downward movement and positioned to have cutting tips thereof engageable with the road surface when in the down position during a scarifying operation, and a plurality of discrete yieldable fluid operated pressure applying means positioned beneath said support frame and directly over said plurality of scarifying blades to apply a downward pressure directly upon said scarifying blades during the sacrifying operation.
 2. The scarifier assembly for engagement with a road surface to excavate the road surface as set forth in claim 1 wherein said plurality of scarifying blade units comprise groups of blades in a row across said support frame, said row being transverse to the direction of travel of said support frame.
 3. The scarifier assembly for assembly with the road surface to excavate the road surface as set forth in claim 1 wherein each of said discrete yieldable pressure units is an air bag.
 4. The scarifier assembly for engagement with the road surface to excavate the road surface as set forth in claim 1 wherein each of said groups of scarifying blades is formed of three rows of three blades in each row aligned transversely to the direction of travel of said support frame and each row staggered from the other rows to allow excavated road material easily to pass through the scarifying blades as it travels in said given direction.
 5. The scarifier assembly for engagement with the road surface to excavate the road surface as set forth in claim 1 further including fluid pressure control means for controlling the pressure produced by each of the said plurality of discrete yieldable pressure units, said pressure control means including means for controlling the fluid pressure produced by the two endmost discrete yieldable pressure units independent of the discrete yieldable units therebetween.
 6. The scarifier assembly for engagement with the road surface to excavate the road surface as set forth in claim 5 wherein said discrete pressure units between said two endmost units are operated from a common pressure supply, and including valve means connected between said common pressure supply and said discrete yieldable pressure units, whereby selected ones of said pressure units can be deactivated.
 7. The scarifier assembly for engagement with a road surface to excavate the road surface as set forth in Claim 1 wherein said scarifying blades include shear pin means for holding said scarifying blades in a fixed position during a scarifying operation and to permit rearward pivotal movement of said scarifying blade when a predetermined high shear pressure is exerted on said scarifying blade.
 8. The scarifier assembly for engagement with a road surface to excavate the road surface as set forth in claim 1 further including joint cutting blade means positioned transversely outwardly of the endmost scarifying blades to remove road resurfacing material from the seam formed along the transverse edges of a repaved road surface to be formed.
 9. The scarifier assembly for engagement with a road surface to excavate the road surface as set forth in claim 1 wherein said scarifying blades each include a cutting tip insert element of hardened metal.
 10. A scarifier assembly for engagement with a road surface to excavate the road surface, comprising: a support frame adapted to be moved over the road surface in a given dIrection, a plurality of scarifying blades secured to said support frame for selective upward and downward movement and positioned to have cutting tips thereof engageable with the road surface when in the down position during a scarifying operation, yieldable pressure applying means positioned beneath said support frame and directly over said plurality of scarifying blades to apply a downward pressure directly upon said scarifying blades during the scarifying operation, a plurality of arm means each having one end pivotally secured to said support frame, said plurality of scarifying blades being arranged in groups, each group secured to the free end of an independent one of said plurality of arm means, a pressure beam secured to said support frame immediately above said free end of said arm means, and pressure bag means positioned between said pressure beam and said free end of said arm means to urge the scarifying blades into the road surface being excavated.
 11. The scarifier assembly for engagement with the road surface to excavate the road surface as set forth in claim 10 further including a plurality of paired spaced apart support plates depending from said free end of said arm means, said scarifying blades being positioned between said support plates, a first fastener of predetermined diameter passing through said support plates and the upper end of said scarifying blade, a second fastener of a diameter less than said predetermined diameter passing through said support plates and said scarifying blade immediately below said first fastener, whereby an excess of pressure applied to said scarifying blade will shear said second diameter fastener and pivot the scarifying blade about said first fastener.
 12. The scarifier assembly for engagement with a road surface to excavate the road surface as set forth in claim 11 further including a plurality of spring means for automatically biasing said arms upwardly to raise the scarifying blade from the road surface when the pressure applying units are deactivated.
 13. The scarifier assembly for engagement with a road surface to excavate the road surface as set forth in claim 12 wherein said spring means are a plurality of discrete leaf springs for each one of said arm means.
 14. A road scarifier apparatus for excavating a road surface comprising in combination: heating means for movement over the road surface to soften asphalt concrete pavement forming the road surface, a support frame for supporting said heating means, said support frame adapted to be moved over the road surface in a given direction, a plurality of scarifying blade units secured to said support frame behind said heating means for separate selective upward and downward movement and positioned to have cutting tips thereof engageable with the heated road surface when in the down position for excavating the road surface, and a plurality of discrete separately yieldable fluid operated pressure applying units positioned beneath said support frame and respectively directly over said plurality of scarifying blade units separately to apply a downward pressure directly upon the scarifying blade units during a scarifying operation.
 15. The road scarifier apparatus for excavating a road surface as set forth in claim 14, further including fluid pressure control means for controlling the pressure produced by each of said yieldable plurality of discrete pressure units, said pressure control means including means for controlling the pressure produced by the two endmost discrete yieldable pressure units independent of the discrete pressure units therebetween.
 16. The road scarifier apparatus for excavating a road surface as set forth in claim 15, wherein said discrete yieldable pressure units between said two endmost units are operated from a common pressure supply, and including valve means connected between said common pressure supply and said discrete yieldable pressure units, whereby selected ones of said pressure units can be de-activated.
 17. The road scArifier apparatus for excavating a road surface as set forth in claim 14, wherein said scarifying blades include shear pin means for holding the scarifying blades in a fixed position during a scarifying operation and to permit rearward pivotal movement of the scarifying blades when a predetermined high shear pressure is exerted on the scarifying blades.
 18. The road scarifier apparatus for excavating a road surface as set forth in claim 14 wherein each of said discrete pressure units is an air bag.
 19. The road scarifier apparatus for excavating a road surface as set forth in claim 14, further including joint cutting blade means positioned transversely outwardly of the endmost scarifying blades to remove the road resurfacing material from the seam formed along the transverse edges of the repaved road surface formed by said apparatus.
 20. The road scarifier apparatus for excavating a road surface as set forth in claim 14, wherein said scarifying blades each include a cutting tip insert element of hard metal.
 21. A road scarifier apparatus for excavating a road surface comprising in combination: heating means for movement over the road surface to soften asphalt concrete pavement forming the road surface, a support frame for supporting said heating means, said support frame adapted to be moved over the road surface in a given direction, a plurality of scarifying blades secured to said support frame behine said heating means for selective upward and downward movement and positioned to have cutting tips thereof engageable with the heated road surface when in the down position for excavating the road surface, yieldable pressure applying means positioned beneath said support frame and directly over said plurality of scarifying blades for applying a downward pressure directly upon the scarifying blades during a scarifying operation, a plurality of arm means each having one end thereof pivotally secured to said support frame, said plurality of scarifying blades being arranged in groups, each group secured to the free end of an independent one of said plurality of arm means, a pressure beam secured to said support frame immediately above said free end of said arm means, and pressure bags positioned between said pressure beam and said free end of said arm means to apply pneumatic pressure between said pressure means and the end of said arm means to urge the scarifying blades into firm contact with the road surface being excavated.
 22. The road scarifier apparatus for excavating a road surface as set forth in claim 21 further including a plurality of paired spaced apart support plates depending from said free end of said arm means, said scarifying blades being positioned between said support plates, a first fastener of predetermined dimension passing through said support plates and the upper end of said scarifying blade, a second fastener of a dimension less than said predetermined dimension passing through said support plates and said scarifying blade immediately below said fastener, whereby an excess of pressure applied to said scarifying blade will shear said second fastener and pivot the scarifying blade about said first fastener.
 23. The road scarifier apparatus for excavating a road surface as set forth in claim 22 further including a plurality of spring means for automatically biasing said arms upwardly to raise the scarifying blades from the road surface when the pressure applying units are de-activated.
 24. The road scarifier apparatus for excavating a road surface as set forth in claim 23, wherein said spring means are a plurality of discrete leaf springs, each leaf spring associated with its associated arm means.
 25. The road scarifier apparatus for excavating a road surface as set forth in claim 15, which includes fluid pressure control means associated with said yieldable pressure control means, said pressure control means having means to control the pressure of the endmost units of the scarifying blades independent of control of the units theRebetween, said control means further including means for deactivating selected ones of said plurality of units including said endmost units of scarifying blades. 